Effect and breeding potential of qSB-11LE, a sheath blight resistance quantitative trait loci from a susceptible rice cultivar

Zuo, S., Yin, Y., Zhang, L., Zhang, Y., Chen, Z., Gu, S., Zhu, L. and Pan, X. 2011. Effect and breeding potential of qSB-11LE, a sheath blight resistance QTL from a susceptible rice cultivar. Can. J. Plant Sci. 91: 191–198. Sheath blight (SB) caused by Rhizoctonia solani is one of the most important diseases of rice worldwide. The QTL qSB-11LE, located on chromosome 11 of an SB-susceptible Oryza japonica rice cultivar Lemont, was identified in previous studies. In this study, its effect on SB resistance and its potential in breeding programs were evaluated using a set of near-isogenic lines (NILs) that exhibit three different genotypes at the qSB-11LE locus and seven backcross populations. Results of field disease evaluation under artificial inoculation showed that the inheritance of resistance of qSB-11LE to SB is controlled by additive gene action and that the genes have a dosage effect on SB resistance. In greenhouse evaluations, the resistance effect of qSB-11LE was expressed at 11 and 14 d after inoculation at the tillering stage. Analysis of field resistance of six BC1F1 populations and one BC2F1 population, developed from the backcrosses between Lemont as the donor parent and six commercial O. indica rice cultivars as recurrent parents, indicated that qSB-11LE could be effectively used to enhance these cultivars’ SB resistance. These observations suggest that the qSB-11LE has considerable potential in rice breeding for resistance to SB, and that its flanking molecular markers could be employed in practical breeding programs for marker-assisted selection.